Archibald david macdonald



(No Model.)

A. D. MACDONALD.

TELEGRAPH RELAY.

No. 551,192. Patented Deo. 10, 1895.

W/TNESSES: /NVENTO/? ARCH/BALD DAVIDMAcOo/VALQ.

A77 ENE).

UNTTED STATES PATENT OIEErcE,

ARCIIIBALD DAVID MACDONALD, OF MELBOURNE, VICTORLA.

TELEGRAPH-RELAY.

SPECIFICATION forming part of Letters Patent No. 551,192, dated December10, 1895.

Application filed November 2, 1894. Serial No. 527,751. (No model.)

To aZZ whom it may concern: I

Be it known that I, AROHIBALD DAVID MAcDoNALD, a subject of the Queen ofGreat Britain and Ireland, and aresident of the Sun Building, QueenStreet, Melbourne, in the Colony of Victoria, Australia, have inventedcertain new and useful Improvements in Methods of and Mechanism forOperating Ar matures of Telegraphic Relays, of which the following is aspecification.

In the ordinary forms of telegraphic relay the principal drawback is thenecessity for frequent readjustment of the instrument as the strength ofthe current varies from time to time, owing to meteorological or otherinfluences. Further, it is found that the current in practice oftenweakens to such an extent that even when adjusted to its limit the relaywill not work so as to produce intelligible signals. Relays in mostgeneral use have the cores, armatures and armature-lever, and regulating-spring arranged in a manner which necessitates unnecessarilystrong currents whether obtained from galvanic cells or other sources)to work such relays. Such currents are as a general rule supplied bymeans of galvanic cells, which are espe cially costly to maintain inconsiderable nu mbers, so that the reduction of the expenses for currenthas become a desideratum.

My improvements relating to the construction of relays are designed toobviate the necessity for-frequent readjustments,and to ren der theemployment feasible of much weaker currents than are ordinarilyemployed, in this way effecting a distinct economy. I11 consequence ofthe mechanism I use being adapted to continue the working whether thecurrent be strong or weak, my instruments will give signals whenordinary ones would fail to do so. Vhen weak currents are used, as Iprefer, the induction troubles now common will practically disappear.Among the economies which may be effected by my said improvements arethe abolition of repeatingstations on many long lines.

The method of regulating my mechanism is by increasing or decreasing thetension of a speeially-arranged spring operating a specially-constructedarmature-lever, but I further have invented a method of causing relayswhen they are found non-responsive to very weak currents to becomesensitive to the same, and so enable workingto be carried on. Thislatter improvement in the method of causing relays to act is applicableto relays generally, but it will require to be brought into use onlyoccasionally-a1. e. when the current has become abnormally weak.

My improvements in mechanism may be applied to relays of various kinds;but for the purpose of making their nature apparent I will now describethem as applied to a simple non-polarized instrument, as shown in thedrawings, in which Figure 1 shows, in perspective, a relay containing myimprovements. Fig. 2 represents a plan view of the same instrument fromabove, and Fig. 3 shows an elevation of it from the rear. Fig. 4 is adiagram showing the apparatus as in application of my said method ofworking relays, and Fig. 5 is a plan view showing contacts.

As will be seen the improvements are in the mechanism for operating thearmature A. In this construction the core and coils B stand upright andthe armature-lever is extended on both sides of its axis or fulcrum IIand so arranged that its arms 0 and D lie horizontally when at rest. Tosecure this result I make the weight of the extension C almost but notquite sufficient to act (when the instrument is free from electrical ormag netic influence) as a counterpoise to the end D, carrying thearmature A. The arm D is extended to Ei. a, considerably beyond thecontactpoints F-and at or near its extremity it is connected tothe lowerend of a spiral vertical spring G, the upper end of which is connectedby a thread or the like to a micrometer or regulating-screw J to enablethe spring-tension to be adjusted. The spring is unlike those ordinarilyused, as it is so arranged that its weight is not a factor in the pullit gives upon the armature, and it is so delicate that a pull of lessthan one grain may be exerted by it on the end of the armature-lever. Apull of about two grains, when there is no current, should cause suchspring to raise the end E until the contactpoint at F is up against thebackstop. This is how the instrument should be seti. 6., with the saidtwo-grain pull lifting E when starting to work it. It is necessary tosee disconnected.

that the armature -lever is horizontal, and when up against theback-stop barely opening the local circuit, so that when the localcircuit is closed the armature shall be as close to the cores aspracticable without touching them.

As work proceeds there is little residual magnetism, so long as thecurrent remains weak; but when the current strengthens the residualmagnetism increases and necessitates a tightening of the verticalspring, (the height of J being regulated by means of the screw N in ahollow post M, in which the bar M is adapted to slide,) until the pullis as great as may be required.

In polarized relays I place the coils 3 with.

their length running horizontally and one core above the other, so as toallow the armature-lever D to oscillate vertically between said cores.The armature orlever for such relay may be constructed and arranged, inrespect to pivoting and counterpoising, as above described for ordinaryrelays, with the agate or back-stop F uppermost, and be furnished with aspecial spring G, also arranged as above set forth. Hitherto such relayshave had no spring and no counterpoise device as applied by me. My saidapparatus thus avoids mechanical impediments to working with weakcurrents and makes the receivinginstruments extremely sensitive, so thatthe speed of signaling is increased.

In the drawings it will be observed that various known parts of relaysare shown, and the use of these will be well understood by personsversed in the art of telegraphy without further reference thereto.

K K are binding-screws for local circuit, and L L binding-screws forconnection of main-line wire, and 0 an upright or supporting frame forparts as shown.

I will now describe in detail my aforesaid method applicable to relaysgenerally.

Then a main-line current is too weak to work a relay at any time in theprocess of working or before working has been established, thesensitiveness of the relay is increased greatly by the following means,viz: I cut off the weak main-line current and momentarily short-circuitthe electromagnet of the relay with, say, one Leclanche' cell, with thesame polarity as the main-line current. This is illustrated in Fig. 4:,which is not to scale, and in which R R shows main line entirelydisconnected from the relay, and S shows a wire connecting one cell T tothe relay X, the latter connection or circuit being made only after themain line R R has been An important point is that the currents fromlines S and R through the relay shall both have the same polarity. Thisis shown in the diagram by the arrows and the arrangement of cells T andY, the former being near and the latter being remote from X. The currentthus passed through the coils is of about six millamperes, four to sixbeing adequate. The telegraph-operator should then work his key and setthe adj ustment low, and then take off the short-circuit cell T andreconnect main line at R R, when it will be found easy to adjust for andwork with weak currents as was required to be done. A much lessdesirable modification of this method would be to introduce a number ofcells, as T, in the short circuit without disconnectin the main-linecurrent, but this course is not so simple. It might require many cellsto be used, and if the ordinary proper number of cells be employed itmight still not be attended with such favorable results as theone-current method above set forth. In some cases, however, this doublecurrent method answers, such current being made to pass through therelay with a combined strength of about four to six millamperes.

When relays are worked after having been at rest sufficiently to enabletheir residual magnetism to be discharged, I find that my above processis greatly superior in its effectiveness to what it would be if it wereapplied to a relay which had not had such rest and which containedresidual magnetism.

Having now particularly described and ascertained the nature of my saidinvention an d in what manner the same is to be performed, I declarethat what I claim is 1. In a relay the combination with anelectro-magnet of a lever fulcrumed at one side of said magnet, andhaving on one side of its fulcrum in successive order an armature,contact points, and a tension spring the latter vertically set above theend of said lever, and On. the other side of said fulcrum an arm orextension of such weight as to act as a counterpoise to the first namedside of the lever and allow the latter to rise against the back stopwhen the said spring is regulated to exert an upward pull substantiallyas and for the purposes set forth.

2. In a polarized relay when at a state of rest a horizontally arrangedpivoted armature lever adapted to oscillate vertically between coresplaced one above another as set forth said lever being fulcrumed on oneside of said cores and having 011 the other side of said cores, contactpoints, and a tension spring the latter vertically set above the end ofsaid lever, and on the other side of said fulcrum an arm or extension ofsuch weight as to act as a counterpoise to the first named side of thelever and allow the latter to rise up against the back stop when thesaid spring is regulated to exert an upward pull substantially as andfor the purposes set forth.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

ARCHIBAIID DAVID MACDONALD.

Witnesses:

GEO. G. TURIs, E. F. NIcHoLLs.

